linux-ext4 - Re: [PATCH 4/5] dax: use sb_issue_zerout instead of calling dax_clear

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Message-ID: <CAPcyv4hcSz7zKXzW3ZtdFbgBLbe0J2oNR-QC2L83adsvU3siFw@mail.gmail.com>
Date:	Tue, 29 Mar 2016 12:37:14 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	"Verma, Vishal L" <vishal.l.verma@...el.com>
Cc:	"linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
	"xfs@....sgi.com" <xfs@....sgi.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	"axboe@...com" <axboe@...com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"Wilcox, Matthew R" <matthew.r.wilcox@...el.com>,
	"david@...morbit.com" <david@...morbit.com>,
	"jack@...e.cz" <jack@...e.cz>
Subject: Re: [PATCH 4/5] dax: use sb_issue_zerout instead of calling dax_clear_sectors

On Tue, Mar 29, 2016 at 11:57 AM, Verma, Vishal L
<vishal.l.verma@...el.com> wrote:
> On Mon, 2016-03-28 at 16:34 -0700, Dan Williams wrote:
>
> <>
>
>> Seems kind of sad to fail the fault due to a bad block when we were
>> going to zero it anyway, right?  I'm not seeing a compelling reason to
>> keep any zeroing in fs/dax.c.
>
> Agreed - but how do we do this? clear_pmem needs to be able to clear an
> arbitrary number of bytes, but to go through the driver, we'd need to
> send down a bio? If only the driver had an rw_bytes like interface that
> could be used by anyone... :)

I think we're ok because clear_pmem() will always happen on PAGE_SIZE,
or HPAGE_SIZE boundaries.
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